Earth-leakage circuit breaker with automatic monitoring capability

ABSTRACT

An earth-leakage circuit breaker has a totalizing current transformer, a magnetic trip device and switchgear with main current contacts for the main leads. A current-signal generator, a current sensor, a time-signal generator and an electronic timer wherein the switching value and response time of the circuit breaker are measured at predetermined intervals, compared with reference switching values and response times and, if these reference values are exceeded, an alarm is promptly given. During the measurement, a locking device prevents the main current contacts from opening and/or when predetermined limiting switching and response times are exceeded, the locking device opens the main current contacts and subsequently acts as a lock preventing the contacts from closing again, which is equivalent to fail-safe behavior. In addition, the switching value of the circuit breaker is multiplied by its response time and the product, which may exceed a particular constant value, is used for monitoring purposes.

BACKGROUND OF THE INVENTION

The invention relates to an error current circuit breaker.

Error current circuit breakers are house wiring devices intended toprotect people from dangerous electric shock and buildings from firescaused by electric wiring. Most of the error current circuit breakers inuse today consist of a housing in which a totalizing or summing currenttransformer, a magnetic relay, a switch gear and a testing means (testkey) are accommodated.

It is known that these devices may fail in the course of time. Thus theelements shown to be most vulnerable are the magnetic relay and thetesting means. An essential feature of the magnetic relay of an errorcurrent circuit breaker is the very small gap between the pole surfacesof its armature and yoke. If after months or years of not being opened,these magnet contacts gradually cold-weld the finely ground polesurfaces, as is known to happen to relays, the response level of theerror current citcuit breaker will gradually rise as well, until theweld (a diffusion welding process) is so firm that there is totaladhesion of the armature to the yoke. Even in complete absence ofpermanent magnet flux, the spring action will then not suffice torelease the armature, unlock the switch gear, and so interrupt thecircuit.

Therefore error current circuit breakers are generally equipped with atest key to be operated manually. There is also a known error currentcircuit breaker with automatic testing (EP A 0,502,393).

Further, GB A 2,056,094 discloses a device for testing error currentcircuit breakers, not intended, however, for installation in the circuitbreaker.

Most known earth-leakage circuit breakers currently operateindependently of the mains voltage (see G. Biegelmeier:"Schutzmassnahmen in Niederspannungs- anlagen" Protective measures inlow-voltage systems!; Osterreichischer Gewerbeverlag, Vienna, 1978), butthere are also so-called DI circuit breakers, which are mains-dependentearth-leakage circuit breakers. Like circuit breakers independent of themains voltage, the DI circuit breakers have a totalizing or summingcurrent transformer with a secondary winding, which is connected tomains-dependent evaluation electronics. The advantage of these circuitbreakers lies in the fact that they do not require any highly sensitivetrip devices, such as the magnetic trip devices. The electronics cansupply any desired insensitive relay, which, in the case of a leakagecurrent, trips the switchgear. The switchgear can even be a contactorcontrolled by this electronics.

Furthermore, European Patent 0,220,408 describes a self-monitoringearth-leakage circuit breaker in which the regular operational test canbe omitted, through the fact that the earth-leakage circuit breakercontinuously monitors itself throughout the whole operating time. Inaddition, the earth-leakage circuit breaker also opens in case ofinterruption of the current supply and does not automatically closeagain when the current supply is resumed. In this case, the monitoringrelates primarily to the electronic circuit. The circuit breaker openswhen the rated non-operate current is exceeded. It is not in a positionto detect an impending defect.

Earth-leakage circuit breakers with both a manually operable test keyand an automatic test key according to German Patent 4,106,652, which,for example, check the mode of operation of the earth-leakage circuitbreaker at monthly intervals, have the disadvantage that only a circuitbreaker that is no longer tripping, i.e., a circuit breaker that is nolonger performing the protective function, is detected. The result ofthis is that the protection does not exist for weeks, and even months,and the circuit breaker fails in an emergency during this period. Addedto this is the fact that only the switching value of the leakage currentis checked.

K. W. Brunner, in the journal Elektrische Maschinen 73, 10-12 (April1994), writes that there are reasons for checking not only the switchingvalues but also the response times for the leakage current. These lie,among other things, in the connection between the body current i_(b) andflow time t in the case of contact with a current-conducting line. Asalready mentioned, Biegelmeier describes this relationship in detail. Italso follows from Diagram 1, which shows the function I.sub.Δ =f(Δt).

The regions of action, shown in the diagram, of a 50/60 Hz alternatingcurrent on the human body, according to IEC Report 479, Chapter 2,Second Edition, are as follows:

Region 1 . . . As a rule, no reaction;

Region 2 . . . As a rule, no pathophysiologically hazardous reaction;

Region 3 . . . Transition region without fixed boundaries. As a rule, noorganic damage; no danger of ventricular fibrillation, but muscularreactions and respiratory complaints with increasing current strengthand duration of action;

Region 4 . . . Increasing probability of ventricular fibrillation (curvec₂ =probability below 5%, curve c₃ =probability below 50%). Withincreasing current strength and duration of action, strongpathophysiological effects, such as cardiac arrest, respiratory arrest,and burns. With respect to ventricular fibrillation, the curves c₁through c₃ relate to longitudinal flow from the left hand to the leftfoot. For durations of actions of less than 200 ms, ventricularfibrillation occurs only in the vulnerable phase, if the thresholdvalues are exceeded.

If the flow time, which is equal to the response time of anearth-leakage circuit breaker, has a value of, for example, 40 ms, thena leakage current of the order of magnitude of 100 to 200 mA, as a rule,does not show any pathophysiologically dangerous action. If, on theother hand, it has a value of ≧100 ms, then a leakage current of 100 to200 mA would be risky for humans. If it were to have a value of ≧500 ms,then 30 mA would already be risky. It is recognized that the product ofthe leakage current and response time is of great importance.

BRIEF SUMMARY OF THE INVENTION

The invention is based on the task of creating an earth-leakage circuitbreaker in which both the switching value and the response time and alsothe product of the two can be checked at regular intervals, either bymanual operation of a key or a switch or completely automatically, andin which an alarm is given when the reference response values areexceeded.

The invention is also based on the task of creating an earth-leakagecircuit breaker for which there is no wait for the detection of adefective circuit breaker, but where an impending defect is alreadydetected before failure of the circuit breaker and an alarm is given ina timely manner, in order to be able to replace the circuit breaker evenbefore its failure.

All known earth-leakage circuit breakers are also burdened by thefollowing disadvantages:

(1) They do not show a fail-safe behavior.

(2) In case of failure of the electrical or electronic control unit,they can not always maintain the earth-leakage protection function.

(3) They do not take into consideration the possibly flowing insulationcurrents, such as, for example, the capacitive leakage currents.

(4) They do not monitor the main current contacts for welding and/or theswitchgear for jamming or the like.

(5) They do not check the opening of the contacts of the magnetic tripdevice.

(6) They do not check the electronic control unit.

The invention is therefore also based on the task of creating anearth-leakage circuit breaker that possesses these additionalproperties.

To detect a leakage current in a mains lead, the earth-leakage circuitbreaker contains a totalizing or summing current transformer, whoseprimary winding is formed by the line conductors. The totalizing currenttransformer also contains a secondary winding in which, upon appearanceof a leakage current in the mains, a signal is formed, which causes theearth-leakage circuit breaker to cut out. In this case, the electricalcircuit is dimensioned such that the circuit breaker cuts out, forexample, within 40 ms at a leakage current of ≦30 mA.

By means of a current-signal generator and current sensor integrated ina microprocessor or microcomputer, a time-signal generator, and anelectronic timer, the switching value and the response time are measuredand/or multiplied by each other, compared with reference values of theswitching currents, response currents, response times, and responseproducts, and, if the reference values are exceeded, a timely alarm isgiven and, during the measurement, an opening of the current contacts isprevented by means of a locking device. This locking device engagesbetween the switchgear and the magnetic trip device, or directly in theswitchgear and prevents the push rod of the magnetic trip device fromactuating the switchgear.

In addition, the locking device is designed such that, whenpredetermined limiting response values are exceeded, it can also serveto open the main current contacts and then serve as a lock preventingthem from closing again, which is equivalent to a fail-safe behavior.

To prevent this lock from blocking the leakage-current protectivefunction in case of a defect in the control electronics, the lockingdevice is drawn out of its locking position, for example, by means of anautomatically self-releasing spring. However, this does not occur aftera fail-safe current switch-off.

If no alarm is given, i.e., the reference response values were notexceeded, then the measured response values are stored and theirincrease is determined during the next measurement (check). From theincrease determined in this way, one can infer the time at which themaximum response values were exceeded, i.e., one can extrapolate anddisplay the time in a suitable manner. As a result, there is sufficienttime to replace the earth-leakage circuit breaker in a timely manner.

The predetermined times after which a measurement process is initiatedare guided by the magnitude of the response values. If the responsevalue approaches the reference value, then the time intervals afterwhich the next measurements are carried out in each case are reducedautomatically.

If not only the response values but also the operability of the wholecircuit breaker is to be monitored, then an alarm is given when aspecific increase in response value is reached. If the circuit breakeris not replaced after that, then it will open automatically after analso predetermined time, e.g., after 6 to 8 weeks.

If a 300-mA earth-leakage circuit breaker, which is used for fireprotection, is involved, 6 to 8 weeks would be much too long, i.e., itmust open immediately if a dangerous increase in the tripping time isreached.

A further possibility for monitoring the whole circuit breaker consistsof not only giving an alarm when the still allowable response time isreached in each case but also opening the main current contacts andreclosing them within 200 ms. In order for the current to continueflowing while the main current contacts are open in this case, auxiliarycurrent contacts close automatically in a bypass-like manner throughthese and reopen after the total checking process (measurement process),i.e., after then reclosing of the main current contacts.

If, however, the main current contacts are not to be checked, because,there were very few cases of failure of the switchgears of theearth-leakage circuit breakers in recent years, because resin-forminglubricants were no longer used, only the trip mechanism, e.g., the triprelay, the magnetic trip device, or an actor of a different type, e.g.,a piezo actor, responds when the response time is reached. During thisprocess, a locking device prevents a tripping of the switchgear. Acurrent failure during the testing process can be also be avoided inthis way.

Because, for example, the magnetic contacts of a magnetic trip devicehave to be closed again immediately after opening, the locking devicehas a special form, so that the magnetic contacts close automaticallywhen the locking device is withdrawn.

The locking device that prevents the unlocking of the switchgear can, ofcourse, also be located at a different suitable position, e.g., in theswitchgear. In this process, the actual locking device can be driven,for example, electromechanically, electromagnetically, electrothermally,by means of conventional actors, an FGL drive, or the like.

Another development of the invention consists of also detecting withthis the increase in the response values of earth-leakage circuitbreakers after a short circuit.

For this purpose, an appropriately dimensioned current sensor detectsthe short-circuit current flowing through the circuit breaker and, bymeans of a suitable device, initiates the measuring processes describedabove. In order to prevent these processes from already taking placeduring overload, it is possible to use, for detection of the shortcircuit, for example, a Rogowski coil, which does not measure theshort-circuit current i.sub.κ, but its rise (di/dt).sub.κ. If thecircuit breaker has suffered damage as a result of the short-circuitcurrent, an alarm is given and/or the main current contact is opened.

All of the hardware resulting from the invention can be developed in theform of a conventional auxiliary switch that can be flange-mounted onthe earth-leakage circuit breaker. It is also meaningful to monitor allfunctions of the earth-leakage circuit breaker according to theinvention by conventional means, e.g., by means of auxiliary contacts,and, in case of failure, i.e., failure of one or more functions, to givean alarm.

This monitoring, and the evaluation of the switching values, can,according to the invention, also be integrated into abuilding-system-engineering system that corresponds with otherearth-leakage circuit breakers via bus lines and that carries out manyof the abovementioned functions in a central manner.

In the monitoring process described above, the limiting response leakagecurrent is set too low, because, normally, certain insulation currentsor capacitive leakage currents flow toward the ground, which falsify thetest leakage currents generated and measured by the monitoringelectronics of the circuit breaker.

This disadvantage is eliminated by the fact that the insulation currentis constantly measured and, in the testing or monitoring process, isautomatically subtracted from the test leakage current. In this way, thelarge fluctuations of the response values caused by these leakagecurrents disappear.

In most earth-leakage circuit breakers, the main current contacts arenot checked although--though extremely rarely--for, example, after shortcircuits, a welding of the main current contacts can take place. Thesame also applies for the jamming of a switchgear. This would cancel theleakage current protective function, i.e., the circuit breaker wouldfail in case of a leakage current.

In order to eliminate this disadvantage as well, the mains voltage isconstantly automatically measured, directly or, for example, via aseries resistor after the contacts and, in case of a leakage current,with non-opening of the main current contacts, a switch-off command isgiven to a welding-resistant switching unit connected in series beforeor after the earth-leakage circuit breaker.

To check for a welding of the main current contacts after a shortcircuit, these must, according to the Invention, open with a time delay,for example, after 20 ms or after the next passage through zero. If theydo not open, then a series-connected switching unit switches off and canno longer be switched on (fail-safe behavior).

The measured signal is also processed for optical and/or acousticalsignalling, or is transmitted to the central station of abuilding-system-engineering system.

Another possibility for checking the switchgear for welding of the maincurrent contacts after a short circuit consists of the following:

Because, after a short circuit, the mains voltage is switched off by thecorresponding automatic cutout, one or more capacitors are required asintermediate energy-storage devices in order to keep the monitoringelectronics of the earth-leakage circuit breaker ready to function.After every short circuit, the leakage current and the response time arechecked and the contacts of the switchgear are opened. This can becarried out by generating a leakage current of the order of magnitude ofthe test leakage current, which causes the magnetic trip device torespond. This opens the switchgear by means of its push rod.

After the circuit breaker has been closed again, the mains voltagemeasurement after the main current contacts of the earth-leakage circuitbreaker indicates whether the contacts are really open. If not, thelocking device now tries to open the contacts. If this is unsuccessful(the mains voltage is still displayed), then a switch in theearth-leakage circuit breaker produces a short circuit, which againtrips the automatic cutout. This is indicated by the earth-leakagecircuit breaker by means of an acoustical and/or optical alarm.

If, against all reason, the automatic cutout should again be closed,then the conductors in the earth-leakage circuit breaker are forcedapart or are cut open by means of one or more insulated cutters.

It has not been described so far how the microprocessor learns that themagnetic trip device trips at the predetermined response values. In thesimplest case, this takes place by means of auxiliary contacts, as iscustomary in automatic-circuit-breaker technology. Light barriers,preferably alternating light barriers (reflected-light barriers) arealso possible. A more elegant possibility consists of measurement andevaluation of the inductive peak current produced in the secondarywinding of the trip device upon opening of the magnetic contacts.

The microprocessor can also correspond with abuilding-system-engineering system. Also, a part of all electronicfunctions, such as comparison, storage, and so on, can be taken over bythe central station of this system.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

The invention, and also its advantageous embodiment, will be explainedin greater detail and described with reference to drawings.

FIG. 1 shows the basic circuit diagram of an earth-leakage circuitbreaker with a test key according to the state of the art;

FIG. 2 shows the basic circuit diagram of an earth-leakage circuitbreakerwith an automatic test key and switchgear lock according toGerman Patent 4,106,652;

FIG. 3 shows the basic circuit diagram of the earth-leakage circuitbreaker in one embodiment of the invention, with a switchgear lock,current-signal generator, current sensor, comparator, operatingamplifier, and signalling equipment;

FIG. 4 shows another basic circuit diagram of the earth-leakage circuitbreaker according to FIG. 3, but with a time-signal generator;

FIG. 5 shows an identical basic circuit diagram of the earth-leakagecircuit breaker according to FIG. 3 without a switchgear lock, but witha bypass and switchgear drive;

FIG. 6 shows the circuit diagram according to FIG. 5, but with anadditional switching unit, which can switch off the current supply mainseven in the case of failure of the earth-leakage circuit breaker;

FIG. 7 shows an exemplifying development of a switchgear lock;

FIG. 8 shows another exemplifying form of the switchgear lock or thelocking device;

FIG. 9 shows the basic circuit diagram of another embodiment of theearth-leakage circuit breaker, with equipment for the detection ofweldings of the main current contacts and a facility for fail-safebehavior; and

FIG. 10 shows a modified circuit diagram of the earth-leakage circuitbreaker with a short-circuit switch and detonating caps or cutters.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a customary two-pole earth-leakage circuit breakeraccording to the state of the art. The two mains leads, outer conductor1 and neutral conductor 2, pass through a totalizing current transformer3 and a switchgear 4. If a leakage current appears, the transformer 3generates a signal causing the response of a trip device 5, which, inturn, opens the switchgear 4 by means of a push rod 6 and therebyinterrupts the current in the mains leads 1 and 2.

In order to be able to check the good working order of the earth-leakagecircuit breaker at regular intervals, a testing device consisting of atest key 7 and a test-resistor 8 is provided. When the test key 7 isdepressed, a leakage current flows through the resistor and opens thecircuit breaker. After the testing process, the circuit breaker must beclosed again manually.

FIG. 2 shows a two-pole earth-leakage circuit breaker with an automatictest key according to German Patent 4,106,652. In this case, anautomatic testing facility 9 is provided, which, shortly before thestart of the automatic testing process, transmits a signal to a controlunit 10, which pushes a locking device 12 between the push rod 6 of thetrip device and the switchgear 4 via a drive 11. This prevents currentinterruption by the switchgear 4, but not the tripping of the tripdevice 5. A monitoring and signalling unit 13 automatically monitors thegood working order of the individual components and also gives an alarmin case the trip unit 5 does not trip.

FIG. 3 shows an exemplifying embodiment of the earth-leakage circuitbreaker, with the following functional groups: In addition to theelements 1 through 13, which were shown in FIG. 2 and have already beenexplained, a current-signal generator 14, a measuring resistor 15, and aunit 16, consisting of a comparator, operational amplifier,measured-value storage unit, and differentiating element ordifferentiator have been added to the circuit. The current-signalgenerator 14 automatically generates an increasing leakage current atpredetermined times, which, after reaching the response value, trips thetrip unit 5. During this process, the locking device 12 prevents ashut-off of the current in the mains leads 1 and 2.

A current sensor, in this case the measuring resistor 15, detects theresponse value by means of a voltage measurement with the use of asample-and-hold circuit. The comparator of the unit 16 also compares thevoltage tapped off from the resistor 15 with the reference responsevalue. All of the response values measured after the predetermined timeintervals are stored in a storage unit. All of these operations can, ofcourse, also be carried out with the use of digital technology.

A differentiator in each case determines the increase in the switchingvalues from the momentary and the preceding values, in order toextrapolate from these to the time of failure of the earth-leakagecircuit breaker. If an impending defect is detected, the monitoring unit13 emits an alarm signal and points to this in a display (not shownhere). In a further development of the invention, the time (date) atwhich the circuit breaker should be replaced appears on the display.

FIG. 4 shows an exemplifying embodiment of the earth-leakage circuitbreaker, without a locking device, which only checks the response timeand contains the following functional groups: transformer 3, switchgear4, trip device 5, push rod 6, load 24, microprocessor 25, and anelectronic circuit breaker 26. At preselectable time intervals, a timerintegrated in the microprocessor 25 measures the response time of theearth-leakage circuit breaker, which essentially consists of atransformer 3, switchgear 4, and trip device 5, as described above.

The measured response time is compared with the reference response timein the microprocessor 25. When the reference value is exceeded, anoptical and/or acoustical alarm is given via an alarm unit (not shown).The microprocessor can, of course, also be included in the central unitof a building-system-engineering system.

A similar procedure is followed with the formation and monitoring of theproduct of the response time and response current. In detail, theautomatic testing process proceeds as follows:

At a time t₁, the microprocessor 25 generates a pulse, with which theelectronic circuit breaker 26 opens. Through a current-limiting resistorincorporated in this circuit breaker, there then flows a preselectableleakage current, which generates a secondary voltage in the transformer3 that actuates the trip device 5. The push rod 6 opens the switchgear4, which closes again within 200 ms by means of a remote control (notshown). Simultaneously with the opening of the switchgear 4, the tripdevice 5 generates a signal that is reported via a line 27 to themicroprocessor 25. If this message does not take place, themicroprocessor increases the time until a response of the trip device 5takes place.

The response time in each case is stored by the microprocessor in anEEPROM, so that the values are not lost in case of current failure. Iftwo or more response times are present, the microprocessor forms theincrease in these (di.sub.α /dt) and optionally extrapolates to the timeat which the reference response time is exceeded. Simultaneously, itgives a silent or loud alarm. If the microprocessor constitutes acomponent of the central unit of a building-system-engineering system,then this reports the time of the expected exceeding of the referenceresponse time. The circuit breaker can be replaced before it can nolonger meet its technical requirements.

FIG. 5 shows an exemplifying embodiment without a locking device, butwith a bypass 17 and a switchgear drive 18.

In this embodiment, not only is the response value of the trip device 5determined, stored, and evaluated, but all components, including theswitchgear 4, its drive 18, and bypass 17 are monitored at the sametime. The mode of operation can be readily derived from the descriptionof FIG. 3.

FIG. 6 shows another exemplifying embodiment similar to that of FIG. 5,but supplemented by a switching device 19. This switches off if theearth-leakage circuit breaker has not been replaced after apredetermined time, determined from the increase in the response value(fail-safe behavior).

FIG. 7, which is made up of four figures, FIG. 7a through FIG. 7d, whichshow one of many conceivable embodiments of the locking device 12 andits drive 11, which, in the case of some of the exemplifying embodimentsmentioned above, inserts itself between the push rod 6 and theswitchgear 4 and, upon withdrawal, automatically closes, for example,the magnetic contacts of the magnetic trip device 5.

In this figure, FIG. 7a represents the starting phase of the monitoringprocess. The push rod 6 of the trip device 5 and the locking device 12are in a stand-by position, i.e., in the retracted state. It can be seenthat the locking device 12, which is spoon-shaped, can shoot past thepush rod 6.

FIG. 7b shows the locking device 12 in a position in which it is nolonger possible to switch off the switchgear 4.

If the response value is now measured and the trip device 5 trips duringthis process, then the push rod 6 will strike against the locking device12, as shown in FIG. 7c.

After completion of the process, the locking device 12 retracts and,with its thickened part, pushes the push rod 6 in a downward direction,as can be seen from FIG. 7d, and the push rod, in turn, recloses themagnetic contacts of the trip device 5.

After closing of the magnetic contacts, the locking device 12 againreturns to its starting position according to FIG. 7a.

The different tasks of the locking device 12 and their executions areshown in FIGS. 8a through 8e.

FIG. 8a shows the locking device 12 with the drive 11 in the startingposition. The main current contacts 4.2 and 4.3 of the switchgear 4,which can separate the mains leads 1, 2, and the magnetic contacts ofthe magnetic trip device are still closed in this case. The push rod 6which can open the switchgear 4 for the purpose of opening the maincurrent contacts 4.2 and 4.3, is also still located in the startingposition.

If the command to initiate the monitoring process is now received fromthe timing clock of the microprocessor, the locking device 12 firstmoves between the trip device 5 and switchgear 4 (FIG. 8b). Immediatelyafter that, the magnetic trip device 5 is tripped and the push rod 6strikes the locking device 12, which prevents the opening of theswitchgear 4 and thus prevents the opening of the main current contacts4.2 and 4.3 (FIG. 8c).

After completion of the monitoring process, the locking device 12retracts and, through its special shape, closes the magnetic contacts ofthe magnetic trip device 5, by pressing the push rod 6 in a downwarddirection (FIG. 8d).

If it has been found during the checking of the switching value and theresponse time that the these are too high in the sense of aleakage-current protection, then the locking device 12 moves throughbetween the switchgear 4 and trip device 5 and thereby opens the maincurrent contacts 4.2 and 4.3, and remains in this position, so that thecontacts can no longer close (FIG. 8e).

If necessary, the magnetic trip device is closed by means of anadditional switching process of the locking device 12, so that themagnetic contacts can not become dirty.

FIG. 9 shows the basic circuit diagram of the earth-leakage circuitbreaker, with a facility for the detection of weldings of the maincurrent contacts and with a fail-safe behavior. The two mains leads,outer conductor 1 and neutral conductor 2, pass through the totalizingcurrent transformer 3 and the switchgear 4. If a leakage currentappears, the transformer 3 generates a signal causing a response of thetrip device 5, which, in turn, opens the switchgear 4 by means of thepush rod 6 and thus interrupts the current in the mains leads 1 and 2.

For the monitoring of the switching value, there is located, connectedto the secondary winding of the totalizing current transformer 3, ameasuring resistor 15, which, like all other components, is connected toa microprocessor 20.

The current-signal generator 14 automatically generates, atpredetermined times, an increasing leakage current, which, afterreaching the response value, causes the trip device 5 to trip. In thiscase the locking device 12, as already described, prevents theswitch-off of the current in the mains leads 1 and 2. A current sensor,in this case the measuring resistor 15, records the response value bymeans of a voltage measurement, for example, with the use of a "sampleand hold circuit." In addition, the comparator of the unit 20 comparesthe voltage picked off from the resistor 15 with the reference responsevalue. All of the response values measured after the predetermined timeintervals are stored in a storage unit. All of these operations are, ofcourse, carried out in the microprocessor 20.

In each case, a differentiator determines the increase in the currentresponse values from the momentary and preceding values, in order toextrapolate from these to the failure time of the earth-leakage circuitbreaker. If an impending defect is detected, the monitoring unit in themicroprocessor 20 gives off an alarm signal and indicates this in adisplay (not shown here). In a further development, the time (date) atwhich the circuit breaker should be replaced appears on the display.

To monitor the response time, the response time of the earth-leakagecircuit breaker is measured at predetermined intervals by means of atime-signal generator integrated in the microprocessor 20, compared witha reference response time, and, if the latter is exceeded, an alarm isgiven.

If no alarm is given, then the measured response time is stored and itsincrease is determined during the next measurement (test). From theincrease determined in this way, the time at which the maximum referenceresponse time is exceeded can be inferred, i.e., it can be determined byextrapolation, and can be displayed in a suitable manner. This resultsin sufficient time for having the earth-leakage circuit breaker replacedin a timely manner.

Because the response time can be different from one circuit breaker toanother--for example, it must have a value of between 0 and 500 ms for"30-mA" circuit breakers--leakage currents of increasing duration areproduced by the microprocessor 20 until these reach the response time.

The predetermined times after which a measuring process is initiated ineach case are guided by the magnitude of the response time. If theresponse time approaches the reference value, then the time intervalsafter which the next measurements are carried out in each case decreaseautomatically.

In order to be able to also indicate the welding of the contacts 4.2 and4.3 after a short circuit, a voltmeter 21 is arranged beyond these,which is also connected to the microprocessor 20.

As already described for FIG. 8e, the locking device 12 is intended toopen the main current contacts 4.2 and 4.3 if, in the check of theswitching value and the response time, it is found that these are toohigh in the sense of a leakage-current protection. If the contacts arewelded or the switchgear is jammed, the fact that the locking device 12is unable to do this is immediately transmitted by the voltmeter 21 tothe microprocessor 20, which causes the opening of the switching device19.

FIG. 10 shows another exemplifying embodiment of the earth-leakagecircuit breaker. If it is found during the automatic checking of theresponse values that these have exceeded their reference values, andthat the circuit breaker has not been replaced despite an optical and/oracoustical warning, then the push rod 6 of the trip device 5 opens thecontacts 4.2 and 4.3 of the switchgear 4. If these are welded or jammed,which is determined by means of the voltmeter 21, then themicroprocessor 20 closes a relay 22 and thereby trips the switching unit19. If, contrary to expectations, this is closed again without replacingthe earth-leakage circuit breaker, then the leads are automaticallycapped with the use of the component 23, which can be carried out, forexample, with the use of an insulated cutter or a miniature detonatingcap.

Various modifications in structure, function or steps may be made to thedisclosed invention by one skilled in the art.

What is claimed is:
 1. Earth-leakage circuit breaker having an automaticmonitoring capability and a current summing transformer, a magnetic tripdevice, and a switchgear having main current contacts for the mainleads, wherein the circuit breaker switching value and response time atpredetermined time intervals is measured by means of a current-signalgenerator, a current sensor, a time -signal generator, and an electronictimer compares these measurements with reference response times andreference response currents and gives a timely alarm when the referencevalues are exceeded, and, during the measurement, prevents opening ofthe main current contacts by means of a locking device wherein thelocking device is designed such that after predetermined limitingresponse values are exceeded opens the main current contacts and canthen act as a lock to prevent the main current contacts from closingagain, which is equivalent to fail-safe behavior.
 2. Earth-leakagecircuit breaker according to claim 1, wherein the switching value ismultiplied by the response time and that the product of the two, whichmust not exceed a specific constant value is used for the monitoring. 3.Earth-leakage circuit breaker according to claim 1 wherein a retractionof the locking device again closes the contacts of the magnetic tripdevice.
 4. Earth-leakage circuit breaker according to claim 1 havingcontrol electronics wherein the locking device, in case of a defect inthe control electronics, is retracted by means of a spring, in order topreserve the leakage current protective function, but not after afail-safe current-protective switching operation.
 5. Earth-leakagecircuit breaker according to claim 1 wherein all of the response valuesmeasured at specific time intervals are stored and, from theautomatically formed increase of the response values with time, the timeat which the reference response values are exceeded is inferred. 6.Earth-leakage circuit breaker according to claim 1 wherein the responsevalue is reached by means of a simulated increasing leakage current,during which the increasing current is generated by means of a rampgenerator.
 7. Earth-leakage circuit breaker according to claim 1 whereinthe length of the predetermined time intervals is guided by themagnitude of the measured response value in each case when the responsevalue approaches the reference value, the time intervals becomeincreasingly shorter.
 8. Earth-leakage circuit breaker according toclaim 1 wherein when a specific value of the increase is reached, eitheror both an alarm is given and the main current contacts are opened andare immediately closed again automatically.
 9. Earth-leakage circuitbreaker according to claim 1 wherein before opening of the main currentcontacts a bypass-similar auxiliary current contacts automaticallyswitch through the main current contacts which open after the reclosingof the main current contacts no current failure takes place. 10.Earth-leakage circuit breaker according to claim 1 wherein the lockingdevice is driven electromechanically or electromagnetically orelectrothermally, with the use of conventional means.
 11. Earth-leakagecircuit breaker according to claim 1 wherein the time that elapsesbefore the earth-leakage circuit breaker is again ready for operation isless than 200 ms.
 12. Earth-leakage circuit breaker according to claim 1wherein the measuring and monitoring facility has the form of anauxiliary switch unit that can be flange-mounted on the earth-leakagecircuit breaker.
 13. Earth-leakage circuit breaker according to claim 1wherein all functions are monitored by by auxiliary contacts, and, incase of failure of one or more functions, an alarm is given. 14.Earth-leakage circuit breaker according to claim 1 wherein themonitoring control and signalling are integrated into abuilding-system-engineering system.
 15. Earth-leakage circuit breakeraccording to claim 1 wherein either a welding or of the main currentcontacts after a short circuit is detected by a measurement of the mainsvoltage by means of a voltage divider or series of resistor beyond thecontacts.
 16. Earth-leakage circuit breaker according to claim 1 whereinafter detection of the non-opening of the main current contacts, aswitching unit connected in series before or after the earth-leakagecircuit breaker switches off.
 17. Earth-leakage circuit breakeraccording to claim 1 wherein after a short circuit as a result ofnatural or circuit originated causes after the opening of an automaticcutout connected in series with the earth-leakage circuit breaker, atime-delayed opening of the main current contacts takes place. 18.Earth-leakage circuit breaker according to claim 1 wherein either orboth a possibly flowing insulation current and capacitive leakagecurrent are subtracted from both the test leakage current and theleakage current.
 19. Earth-leakage circuit breaker according to claim 1wherein either or both the insulation current and the capacitive leakagecurrent are constantly monitored.
 20. Earth-leakage circuit breakeraccording to claim 1 wherein to check the opening of the magnetic tripdevice a peak inductive current that is produced in a coil of the tripdevice during opening of the magnetic contacts is measured andevaluated.
 21. Earth-leakage circuit breaker according to claim 1wherein a defect in the control electronics is displayed by a red LED.22. Earth-leakage circuit breaker according to claim 1 wherein amicroprocessor or a microcomputer monitors the switching values,response times, and the product of the two and takes over all otherelectronic functions.
 23. Earth-leakage circuit breaker according toclaim 1 wherein the whole monitoring process is carried outautomatically.
 24. Earth-leakage circuit breaker according to claim 1wherein the circuit breaker can only be closed again if either or bothan automatic cutout and an additional switching unit have beenpreviously closed and at the mains voltage.
 25. Earth-leakage circuitbreaker according to claim 1 wherein in case of a failure of the maincurrent contacts, a switch produces a short circuit that trips anautomatic cutout connected in series before or after the switch. 26.Earth-leakage circuit breaker according to claim 22 wherein after theopening of the automatic cutout, at least one intermediate energystorage unit is available, which keeps the monitoring electronics readyfor operation.
 27. Earth-leakage circuit breaker according to claim 1wherein in an emergency situation, the main leads are opened by means ofone or more insulated cutters or are separated by means of a miniaturedetonating cap.
 28. Earth-leakage circuit breaker according to claim 1wherein in case of failure of the leakage-current protection functionthe main leads are separated by force by means of insulated cutters orwith a miniature detonating cap.